# Eclipse Probability

In the spirit of the recent total eclipse, I have a question about its happening.

Given that a natural satellite (e.g. moon) can only be sustained in a certian orbital range without crashing into Earth or being flung into the rest of space and given that the moon we have gives a pretty good approximation of total solar coverage during a total eclipse, what are the odds that a natural satellite randomly placed in the aforementioned orbital range will produce such a coverage during an eclipse?

This assumes that if the moon is further away from the earth, it will cover more of the sun … and if it is closer it would only cover part of it (like a dime on a quarter).

This also assumes that the randomly place satellite will cross the sun’s path at some point.

Just curious :}

{{{This assumes that if the moon is further away from the earth, it will cover more of the sun … and if it is closer it would only cover part of it (like a dime on a quarter).}}}—Skott

## Uh, small problem here. You’ve got it reversed.

Kalél
(The Original EnigmaOne)
Common ¢ for all ages.

Other way around move the moon closer to cover more. Do the dime and quarter you’ll see. Lot of random assumption there. Not sure I understand what you are asking. As you stated totallity has to do with the size and distance of the satellite. the distance has to do with its speed Basically orbiting ,in this sense ,is freefalling around a gravitational center.so you got your G and your Mass and your rate and your distance all working together.Put any random sized object at the right distance in the right plane and eclipse. You should be able to ‘eclipse’ the sun with that quarter. ( do not look directly at the retina you will give the dime a sun burn) Are you asking if other planets have total eclipses? Don’t know, possibly Pluto has several. Venus an d mercury pass between us (occlude) and the sun. They are bigger than our moon just too far away to eclipse it. Or maybe not.

So you caught me writing a question while the majority of my mind was focused on programming. You’re right… I got them backwards. My apologies.

I guess I had also assumed that the randomly placed satellite would be the same size as our current moon and have the same velocity.

It just seems amazing to me that our only natural satellite is placed just right so that it covers the sun rather perfectly during an eclipse.

It doesn’t always do that at every eclipse - of course it depends on its distance from Earth at the time, hence the phenomenon of annular eclipses. Still pretty damn cool though.
Since we’re on the subject, I saw the BBC video of the eclipse this morning and was pretty impressed. The first moment of totality was hella dramatic - like someone had hit the switch at the right second and turned on the light show. My question is this - was that just the camera getting used to the lower level of light, thus making it appear like it suddenly shone out, or is that what people actually can see?

Cave Diem! Carpe Canem!

That light show is the sun’s corona: a region of glowing gas that extends out from the sun and constitutes the sun’s “outer atmosphere”. You can’t see it ordinarily because it’s very faint compared to the sun’s disk. That’s why astronomers love solar elcipses, so they can get a good look at the corona.

I know it’s the corona I’m still an amateur astronomy buff. I’m referring to the apparent effect of the corona suddenly appearing to switch on as totality is achieved. Let me see if I can post the link.

http://news.bbc.co.uk/olmedia/415000/video/_417322_totality_vi.ram

At about the 1:09 mark, you’ll see the crescent of the fading sun dim into blackness, and then the corona blazing forth out of seeming nothingness like a switch was thrown. What I want to know is, is that an effect visible to the naked eye?

Cave Diem! Carpe Canem!

The only eclipse i have seen in person wasn’t total. Way back in the 60’s I think ,in Texas panhandle and I don’t remember pecentage covered relativly high i think.(anybody?) I was standing under a tree because I noticed that while we were all trying to focus the cards with the hole poked in them, the spaces between the leaves were focusing thousands of them on the ground. I lokked around at the maximum coverage and it seemed to get darker suddenly rather than gradually. It is nice that the moon is exactly positioned . I would like to thank whoever is responsible.

The answer to the OP is that the earth and the moon share a rather unique relationship with respect to the size of the bodies. It is this, more than the orbit, that causes eclipses. In other words, any natural satellite might transit the planet’s star (just as Mercury does in our solar system), but only a body of a specific size will actually eclipse the star. Given that for life as we know it to exist, a planet must be located within a particular distance from its star, the trick is for that planet to have a satellite of sufficient size to cover the apparent size of the stellar disk as seen from the planet’s surface.